Systems and methods for ablation of tissue

ABSTRACT

A system for treating tissue includes a probe assembly having a cannula, a shaft, and one or more needle electrodes. The shaft has a distal end, a proximal end, and a lumen extending between the distal and proximal ends of the shaft, and is slidable within the lumen of the cannula. Each needle electrode has a lumen that may be placed in communication with a port at a proximal end of the probe assembly, and is configured to deliver an occlusive element to a site. The system may further include an embolization actuator for delivering the occlusive element. A method of treating tissue includes placing an electrode at a site of a treatment region, occluding at least a part of a vessel located adjacent the site by delivering an occlusion element from an electrode, and delivering ablation energy to the site while the vessel is at least partially occluded.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to medical devices, and moreparticularly, to systems and methods for ablating or otherwise treatingtissue using electrical energy.

2. Background of the Invention

Tissue may be destroyed, ablated, or otherwise treated using thermalenergy during various therapeutic procedures. Many forms of thermalenergy may be imparted to tissue, such as radio frequency electricalenergy, microwave electromagnetic energy, laser energy, acoustic energy,or thermal conduction.

In particular, radio frequency ablation (RFA) may be used to treatpatients with tissue anomalies, such as liver anomalies and many primarycancers, such as cancers of the stomach, bowel, pancreas, kidney andlung. RFA treatment involves destroying undesirable cells by generatingheat through agitation caused by the application of alternatingelectrical current (radio frequency energy) through the tissue.

Various RF ablation devices have been suggested for this purpose. Forexample, U.S. Pat. No. 5,855,576 describes an ablation apparatus thatincludes a plurality of wire electrodes deployable from a cannula. Eachof the wires includes a proximal end that is electrically coupled to agenerator, and a distal end that may project from a distal end of thecannula. The wires are arranged in an array with the distal ends locatedgenerally radially and uniformly spaced apart from the catheter distalend. The wires may be energized in a monopolar or bipolar configurationto heat and necrose tissue within a precisely defined volumetric regionof target tissue. Such devices may be used either in open surgicalsettings, in laparoscopic procedures, and/or in percutaneousinterventions.

Generally, ablation therapy uses heat to kill tissue at a target site.The effective rate of tissue ablation is highly dependent on how much ofthe target tissue is heated to a therapeutic level. In certainsituations, complete ablation of target tissue that is adjacent a vesselmay be difficult or impossible to perform, since significant bloodflowmay draw the produced heat away from the vessel wall, resulting inincomplete necrosis of the tissue surrounding the vessel. Thisphenomenon, which causes the tissue with greater blood flow to be heatedless, and the tissue with lesser blood flow to be heated more, is knownas the “heat sink” effect. It is believed that the heat sink effect ismore pronounced for ablation of tissue adjacent large vessels that aremore than 3 millimeters (mm) in diameter. Due to the increasedvascularity of the liver, the heat sink effect may cause recurrence ofliver tumors after a radio frequency ablation.

Accordingly, improved systems and methods for ablating tissue would beuseful.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a system fortreating tissue is provided that includes a probe assembly and/or anembolization actuator. The probe assembly includes a shaft carrying oneor more electrodes. In one embodiment, the electrodes are needleelectrodes. At least one of the needle electrodes has an electrodelumen. The shaft has a distal end, a proximal end, and a lumen extendingbetween the distal and proximal ends of the shaft. In one embodiment,the probe assembly further includes a cannula having a distal end, aproximal end, and a lumen extending between the distal and proximalends. The shaft may be slidable within the lumen of the cannula. In oneembodiment, the shaft includes a plurality of delivery lumens. In thiscase, each needle electrode has a lumen that may be in fluidcommunication with the delivery lumen of the shaft. In anotherembodiment, the shaft includes a single lumen, and each needle electrodemay extend proximally through the entire length of the shaft within theshaft lumen.

The needle electrodes may be used to ablate tissue and/or deliver anocclusion element to a site, such as a vessel. By way of non-limitingexamples, the occlusion element may include an embolic coil, liquidembolic, an occlusion balloon, embolic particles, and a filter. In oneembodiment, the needle electrodes have sharp distal tips that allow thetubular electrodes to penetrate tissue, such as a wall of a vessel. Theprobe assembly may further include one or more radio-opaque markerssecured to one or all of the needle electrodes.

The embolization actuator may include a variety of devices, the type ofwhich depends on the type of occlusion element used. By way ofnon-limiting examples, for delivery of embolic coil, the embolizationactuator may include an elongate member, such as a guidewire fordistally advancing the embolic coil within the electrode lumen. Fordelivery of liquid embolic, the embolization actuator may include asyringe or a pump for delivering the liquid embolic. For delivery ofembolic particles, the embolization actuator may include a plunger.Alternatively, if the embolic particles are delivered within a solution,the embolization actuator may include a syringe, a pump, and/or thesolution. Other types of embolization actuator are also described.

The probe assembly may also include an indexer, or a handle memberhaving indexing capability, that is secured to the proximal end of theshaft. The handle allows a user to select which of the needle electrodesis used to deliver the occlusion element. In one embodiment, the handlemember may include a port and may be rotated about a longitudinal axisof the tubular member such that the port is in fluid communication withone of the delivery lumens and/or the electrode lumens. The handlemember and/or the shaft may include a marker to indicate an orientationor a position of the handle relative to the shaft. One or more occlusionelements may be inserted into the port of the handle, and distallyadvanced through the lumen of the tubular section and through the lumenof the needle electrode to a site.

In another embodiment, the probe assembly includes an indexer that isplaced within the lumen of the shaft. The indexer includes a lumen andmay be rotated about a longitudinal axis of the tubular member such thatthe lumen of the indexer may be in fluid communication with the lumen ofone of the needle electrodes. The indexer and/or the shaft may include amarker to indicate an orientation or a position of the indexer relativeto the shaft. One or more occlusion elements may be inserted into thelumen of the indexer and distally advanced through the lumen of theneedle electrode to a site.

In accordance with another aspect of the invention, a medical probeassembly includes an elongated shaft, a plurality of tissue penetratingelements carried by the elongated shaft, a port carried by the elongatedshaft, and an indexer carried by the elongated shaft. Each of theplurality of tissue penetrating elements includes a lumen. The indexeris configured for selectively placing the port in communication with thelumen of one of the tissue penetrating elements.

In accordance with yet another aspect of the invention, a system ofoccluding blood flow includes a probe assembly having an inlet and aplurality of outlet ports, an indexer configured for selectively placingthe inlet port in communication with one of the outlet ports, and anembolization actuator for delivering an occlusion element through theinlet port.

In accordance with another aspect of the invention, a tissue ablationsystem includes a probe assembly having one or more ablation electrodes,and an embolization actuator. The one or more electrodes each has alumen. The embolization actuator is configured to be in communicationwith at least one of the electrode lumens.

In accordance with another aspect of the present invention, a method isprovided for treating tissue at a treatment region. The method oftreating tissue includes inserting an occlusion electrode through a wallof the vessel, delivering an occlusion element from the electrode into alumen of the vessel to at least partially occlude the flow of bloodthrough the vessel, and delivering ablation energy to the tissue whilethe vessel is at least partially occluded.

Other aspects and features of the invention will be evident from readingthe following detailed description of the preferred embodiments, whichare intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how advantagesand objects of the present inventions are obtained, a more particulardescription of the present inventions briefly described above will berendered by reference to specific embodiments thereof, which areillustrated in the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered limiting its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings.

FIG. 1 is a block diagram of a tissue ablation system constructed inaccordance with an embodiment of the present invention;

FIG. 2 is a side view of an ablation probe assembly used in the tissuetreatment system of FIG. 1, wherein a needle electrode array isparticularly shown retracted;

FIG. 3 is a side view of an ablation probe assembly used in the tissuetreatment system of FIG. 1, wherein the needle electrode array isparticularly shown deployed;

FIG. 4 is a partial cross-sectional side view of the probe assembly ofFIG. 3;

FIG. 5 is a cross-sectional end view of the proximal end of the probeassembly of FIG. 4;

FIGS. 6A and 6B are cross-sectional side and end views, respectively, ofa handle of the probe assembly of FIG. 2;

FIGS. 7A–7E are partial cross-sectional views of the distal end of oneof the needle electrodes, particularly showing variations of usage ofthe needle electrode;

FIG. 8A is a partial cross-sectional side view of another ablation probeassembly that can be used in the ablation system of FIG. 1;

FIG. 8B is a cross-sectional end view of the probe assembly of FIG. 8A;and

FIGS. 9A–9E illustrate cross-sectional views of one preferred method ofusing the tissue treatment system of FIG. 1 to treat target tissue;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a tissue ablation system 2 constructed in accordancewith a preferred embodiment of the present inventions. The tissueablation system 2 generally comprises a probe assembly 4 configured forintroduction into the body of a patient for ablative treatment of targettissue. The tissue ablation system 2 also includes a radio frequency(RF) generator 6 configured for supplying RF energy to the probeassembly 4 in a controlled manner, and an embolization actuator 8 fordelivering occlusive element(s) 9 to a site, such as a blood vessel, sothat a more efficient and effective ablation treatment is effected.

Referring specifically now to FIGS. 2 and 3, the probe assembly 4generally comprises an elongated cannula 12, a shaft 20 slidablydisposed within the cannula 12, and a plurality of electrodes 26 carriedby the shaft 20. The cannula 12 has a distal end 14, a proximal end 16,and a central lumen 18 extending through the cannula 12 between thedistal end 14 and the proximal end 16. As will be described in furtherdetail below, the cannula 12 may be rigid, semi-rigid, or flexibledepending upon the designed means for introducing the cannula 12 to thetarget tissue. The cannula 12 is composed of a suitable material, suchas plastic, metal or the like, and has a suitable length, typically inthe range from 5 cm to 30 cm, preferably from 10 cm to 20 cm. Ifcomposed of an electrically conductive material, the cannula 12 ispreferably covered with an insulative material. The cannula 12 has anoutside diameter consistent with its intended use, typically being from1 mm to 5 mm, usually from 1.3 mm to 4 mm. The cannula 12 has an innerdiameter in the range from 0.7 mm to 4 mm, preferably from 1 mm to 3.5mm. The cannula 12 may also have other outside and inner diameters.

The shaft 20, which may be a surgical probe shaft, comprises a distalend 22 and a proximal end 24. Like the cannula 12, the shaft 20 iscomposed of a suitable material, such as plastic, metal or the like. Itcan be appreciated that longitudinal translation of the shaft 20relative to the cannula 12 in a distal direction 40 deploys the needleelectrodes 26 from the distal end 14 of the cannula 12 (FIG. 3), andlongitudinal translation of the shaft 20 relative to the cannula 12 in aproximal direction 42 retracts the shaft 20 and the needle electrodes 26into the distal end 14 of the cannula 12 (FIG. 2).

Referring to FIGS. 4 and 5, the shaft 20 further comprises a pluralityof delivery lumens 72 extending from its proximal end 24 to its distalend 22. In one embodiment, each electrode 26 is a needle electrode,which resembles the shape of a needle or wire. However, the electrodes26 may also have other shapes as well. As will be described in furtherdetail below, the lumens 72 provide a means for delivering one or moreocclusive elements from the needle electrodes 26. In the illustratedembodiment, the lumens 72 are composed of separate tubes 70 that aredisposed within a main lumen 25 of the shaft 20. Alternatively, thelumens 72 can be formed within the shaft 20 itself, e.g., by forming theshaft 20 and lumens 72 from a single extrusion.

In the illustrated embodiment, the proximal ends 62 of the electrodes 26are secured to the distal end 22 of the shaft 20, e.g., by a weld,brazing, a glue, or other suitable adhesive, depending on the materialsfrom which the electrode 26 and the shaft 20 are made. Each of theelectrodes 26 comprises a lumen 64 that is in communication with arespective lumen 72 of the shaft 20, and an opening or outlet port 68from which an occlusive element 9 may exit, as will be described infurther detail below.

Each of the individual needle electrodes 26 is in the form of a smalldiameter metal element, which can penetrate into tissue as it isadvanced from a target site within the target region. When deployed fromthe cannula 12, the array 27 of needle electrodes 26 is placed in athree-dimensional configuration that usually defines a generallyellipsoidal or spherical volume having a periphery with a maximum radiusin the range from 0.5 to 3 cm. The needle electrodes 26 are resilientand pre-shaped to assume a desired configuration when advanced intotissue. In the illustrated embodiment, the needle electrodes 26 divergeradially outwardly from the cannula 12 in a uniform pattern, i.e., withthe spacing between adjacent needle electrodes 26 diverging in asubstantially uniform and/or symmetric pattern. In the illustratedembodiment, the needle electrodes 26 also evert proximally, so that theyface partially or fully in the proximal direction when fully deployed.In exemplary embodiments, pairs of adjacent needle electrodes 26 can bespaced from each other in similar or identical, repeated patterns andcan be symmetrically positioned about an axis of the shaft 20. It willbe appreciated that a wide variety of particular patterns can beprovided to uniformly cover the region to be treated. It should be notedthat although a total of six needle electrodes 26 are illustrated inFIG. 3, additional needle electrodes 26 can be added in the spacesbetween the illustrated needle electrodes 26, with the maximum number ofneedle electrodes 26 determined by the electrode width and totalcircumferential distance available (i.e., the needle electrodes 26 couldbe tightly packed). It should be noted that the shape and spacing of theneedle electrodes 26 should not be limited to that described previously,and that the needle electrodes 26 may have other pre-formed shapes andmay be spaced from each other in a non-uniform pattern.

Each individual needle electrode 26 is preferably composed of a singletubular wire that may be composed from a variety of elastic materials.Very desirable materials of construction, from a mechanical point ofview, are materials which maintain their shape despite being subjectedto high stress. Certain “super-elastic alloys” include nickel/titaniumalloys, copper/zinc alloys, or nickel/aluminum alloys. Alloys that maybe used are also described in U.S. Pat. Nos. 3,174,851, 3,351,463, and3,753,700, the disclosures of which are hereby expressly incorporated byreference. The needle electrode 26 may also be made from any of a widevariety of stainless steels. The needle electrode 26 may also includethe Platinum Group metals, especially platinum, rhodium, palladium,rhenium, as well as tungsten, gold, silver, tantalum, and alloys ofthese metals. These metals are largely biologically inert. They alsohave significant radiopacity to allow the needle electrodes 26 to bevisualized in-situ, and their alloys may be tailored to accomplish anappropriate blend of flexibility and stiffness. They may be coated ontothe needle electrodes 26 or be mixed with another material used forconstruction of the needle electrodes 26. The needle electrodes 26 mayhave circular or non-circular cross-sections, but preferably haverectilinear cross-sections. In this manner, the needle electrodes 26 aregenerally stiffer in the transverse direction and more flexible in theradial direction. By increasing transverse stiffness, propercircumferential alignment of the needle electrodes 26 within the lumen18 of the cannula 12 is enhanced. Exemplary needle electrodes will havea width (in the circumferential direction) in the range from 0.2 mm to0.6 mm, preferably from 0.35 mm to 0.40 mm, and a thickness (in theradial direction) in the range from 0.05 mm to 0.3 mm, preferably from0.1 mm to 0.2 mm.

The distal ends 66 of the needle electrodes 26 may be honed or sharpenedto facilitate their ability to penetrate tissue. The distal ends 66 ofthese needle electrodes 26 may be hardened using conventional heattreatment or other metallurgical processes. They may be partiallycovered with insulation, although they will be at least partially freefrom insulation over their distal portions.

The needle electrodes 26 are electrically coupled to the distal end 22of the shaft 20. This can be accomplished in a variety of manners, butin the illustrated embodiment, the electrodes 26 are coupled to thedistal end 22 of the shaft 20 via intermediate electrical conductors,such as wires (not shown), that can be disposed within a wall, mainlumen 25 or delivery lumens 72 of the shaft 20. Alternatively, the shaft20 and any component between the shaft 20 and the needle electrodes 26,are composed of an electrically conductive material, such as stainlesssteel, and may therefore conveniently serve as intermediate electricalconductors. Even more alternatively, the needle electrodes 26 mayproximally extend the entire distance of the shaft 20, in which case,the delivery lumens 72 may not be necessary.

Each electrode 26 may also include a radio-opaque marker 66 and/or asensor (not shown) carried at the distal end 60 of the electrode 26. Thesensor may be used to sense a characteristic, such as the impedance orthe temperature, of tissue being ablated. In one embodiment, eachelectrode 26 may have a radio-opaque marker having a differentconfiguration (i.e., shape, geometry, size) that is different fromothers. This allows identification of the electrodes 26.

In the illustrated embodiment, the RF current is delivered to theelectrode array 27 in a monopolar fashion, which means that current willpass from the electrode array 27, which is configured to concentrate theenergy flux in order to have an injurious effect on the surroundingtissue, and a dispersive electrode (not shown), which is locatedremotely from the electrode array 27 and has a sufficiently large area(typically 130 cm² for an adult), so that the current density is low andnon-injurious to surrounding tissue. In the illustrated embodiment, thedispersive electrode may be attached externally to the patient, e.g.,using a contact pad placed on the patient's flank. In a monopolararrangement, the needle electrodes 26 are bundled together with theirproximal portions having only a single layer of insulation over thecannula 12.

Alternatively, the RF current is delivered to the electrode array 27 ina bipolar fashion, which means that current will pass between twoelectrodes (“positive” and “negative” electrodes). In a bipolararrangement, the positive and negative needle electrodes will beinsulated from each other in any regions where they would or could be incontact with each other during the power delivery phase.

Returning to FIGS. 2 and 3, the probe assembly 4 further comprises ahandle assembly 27, which includes a member 28 mounted to the proximalend 24 of the shaft 20, and an handle sleeve 29 mounted to the proximalend 16 of the cannula 12. The handle member 28 is slidably engaged withthe handle sleeve 29 (and the cannula 20). The handle member 28 alsocomprises an electrical connector 38 in which the proximal ends of theneedle electrodes 26 (or alternatively, intermediate conductors) arecoupled. The handles member 28 and the handle sleeve 29 can be composedof any suitable rigid material, such as, e.g., metal, plastic, or thelike.

FIGS. 6A and 6B, the handle member 28 includes a delivery or inlet port100, which is configured to be in fluid communication with one of thedelivery lumens 72 for delivery of the occlusive element 9. In thiscase, the electrode lumen 64 would be in indirect fluid communicationwith the delivery port 100. Alternatively, if the needle electrodes 26proximally extend the entire distance of the shaft 20, the delivery port100 may be configured to be in direct fluid communication with one ofthe electrode lumens 64. In the illustrated embodiment, the handlemember 28 has a recess 103 that is adapted to mate with a protrusion 104of the shaft 20, thereby rotatably securing the handle member 28 to theproximal end 24 of the shaft 20. In this case, a user may rotate thehandle member 28 about a longitudinal axis 106 to selectively choosewhich of the delivery lumens 72, and therefore, which of the lumens 64of the electrodes 26, with which the port 100 is in communication. Assuch, the handle member 28 serves as an indexer for selecting one of theelectrodes 26. The handle member 28 also includes an electrical port 102housing the electrical connector 38. Alternatively, the electricalconnector 38 may be located on the proximal end 24 of the shaft 20distal to the handle member 28. In this case, the electrical port 102 ofthe handle member 28 may not be necessary. Optionally, a marker (notshown) may be placed on the handle member 28 and/or on the proximal end24 of the shaft 20 for indicating a rotational orientation or a positionof the handle member 28 relative to the shaft 20 (and the electrodes 26)during use.

In another embodiment, instead of coupling the handle member 28 to theshaft 20 using the recess 103 and the protrusion 104, the handle member28 may be configured to slidably engage the shaft 20. In this case, theshaft 20 may include a plurality of slots disposed on the exteriorsurface of the shaft 20, and the handle member 28 may include anindexing key that can mate with the respective slots on the shaft 20 asthe handle member 28 is axially advanced relative to the shaft 20. Suchindexing feature allows better alignment of the delivery port 100 with adesired shaft lumen 72. Angle indexing devices that may be used includethose described in U.S. patent application Ser. No. 10/317,796, entitled“Angle Indexer For Medical Devices”, the entire disclosure of which isexpressly incorporated by reference herein. In another embodiment, thehandle member 28 may also include a locking mechanism (not shown) totemporarily lock against the shaft 20 to provide a more stable indexing.For example, the locking mechanism may include an axially-sliding clutchassembly that is slidable along an axis of the shaft 20 to therebysecure the handle member 28 against the shaft 20. Other securing devicesknown in the art may also be used.

Referring back to FIG. 1, the RF generator 6 is electrically connectedto the electrical connector 38, which as previously described, may bedirectly or indirectly electrically coupled to the electrode array 27.The RF generator 6 is a conventional RF power supply that operates at afrequency in the range from 200 KHz to 1.25 MHz, with a conventionalsinusoidal or non-sinusoidal wave form. Such power supplies areavailable from many commercial suppliers, such as Valleylab, Aspen, andBovie. Most general purpose electrosurgical power supplies, however,operate at higher voltages and powers than would normally be necessaryor suitable for vessel occlusion. Thus, such power supplies wouldusually be operated at the lower ends of their voltage and powercapabilities. More suitable power supplies will be capable of supplyingan ablation current at a relatively low voltage, typically below 150V(peak-to-peak), usually being from 50V to 100V. The power will usuallybe from 20 W to 200 W, usually having a sine wave form, although otherwave forms would also be acceptable. Power supplies capable of operatingwithin these ranges are available from commercial vendors, such asRadioTherapeutics of San Jose, Calif., who markets these power suppliesunder the trademarks RF2000 (100 W) and RF3000 (200 W).

Further details regarding needle electrode array-type probe arrangementsare disclosed in U.S. Pat. No. 6,379,353, entitled “Apparatus and Methodfor Treating Tissue with Multiple Electrodes,” which is hereby expresslyincorporated herein by reference.

As previously described, the system 2 is designed to deliver one or moreocclusive elements 9 within a blood vessel. The specific design of theneedle electrodes 26 (e.g., the cross-section of the needle electrodes26) and the embolization actuator 8 will depend upon the occlusiveelements 8 that are to be delivered within the blood vessel. FIGS. 7A–7Eshow examples of the types of embolization actuators 8 and occlusionelements 9 that may be delivered by a needle electrode 26.

FIG. 7A shows the needle electrode 26 delivering an embolic coil 160(the occlusive element 9) from the outlet port 68 to a site. The emboliccoil 160 may be detachably coupled to an elongate member 162, such as apusher wire, a core wire, or a guide wire by a joint 164. In this case,the embolization actuator 8 includes the elongate member 162, which maybe used to distally advance the embolic coil 160 within one of theelectrode lumens 64. The embolic coil 160 may have a variety of primaryshapes, secondary shapes, and/or tertiary shapes. Embolic coil designs,and methods of making such, are described in U.S. Pat. No. 6,322,576B1to Wallace et al., the entirety of which is incorporated by referenceherein. In one embodiment, the embolic coil 160 is stretched into a lowprofile when resided within the lumen 64 of the electrode 26, andassumes a three-dimensional configuration when outside the lumen 64. Theembolic coil 160 may be detachable by electrolytic means such asdescribed in U.S. Pat. Nos. 5,234,437, 5,250,071, 5,261,916, 5,304,195,5,312,415, and 5,350,397, the disclosures of which are expresslyincorporated by reference herein. It will be appreciated that mechanicaljoints, and other types of detachable joints known in the art forplacing occlusive elements in a site may alternatively be used to couplethe occlusion coil 160 to the elongate member 162. Examples of suchmechanical joints may be found in U.S. Pat. No. 5,234,437, to Sepetka,U.S. Pat. No. 5,250,071 to Palermo, U.S. Pat. No. 5,261,916, toEngelson, U.S. Pat. No. 5,304,195, to Twyford et al., U.S. Pat. No.5,312,415, to Palermo, and U.S. Pat. No. 5,350,397, to Palermo et al,the disclosures of which are expressly incorporated herein by reference.

FIG. 7B shows the needle electrode 26 delivering liquid embolic 168 (theocclusive element 9) to a site. In the illustrated embodiment, theliquid embolic 168 is delivered by the lumen 64 of the needle electrode26 out through the outlet port 68. Alternatively, the liquid embolic 168may be delivered by one or more tubular delivery members that arepositioned within the lumen 64 of the electrode 26. Examples of liquidembolic that may be used are described in U.S. Pat. Nos. 6,139,520 and6,152,943, the entireties of which are expressly incorporated herein byreference. U.S. Pat. No. 6,139,520 discloses a cross linkedpolysaccharide fiber formed by combining a first liquid includingpolysaccharide and a second liquid including an ionic cross linkingagent. U.S. Pat. No. 6,152,943 discloses a polymer formed by twocomponents. Delivery of the liquid embolic 168 may be accomplished byusing the embolization actuator 8, which in this case may be a syringe,a pump, or other devices known for delivering fluid. Particularly, theembolization actuator 8 may be used to apply pressure within the shaftlumen 72 and/or the lumen 64 of the needle electrode 26 to assistdelivery of the liquid embolic 168. If the handle member 28 is used, theembolization actuator 8 may be coupled to the delivery port 100 of thehandle member 28. For example, the embolization actuator may be coupledto the handle member 28 so that the embolization actuator 8 can beplaced in communication with one of the needle lumen 64 or one of theshaft lumens 72.

FIG. 7C shows the needle electrode 26 delivering embolic particles 170(the occlusive element 9) to a site. In the illustrated embodiment, theembolic particles 170 are delivered by the lumen 64 of the needleelectrode 26 out through the outlet port 68. The embolization actuator8, which in this case may include a plunger, may be used to distallyadvance the embolic particles 170 within one of the electrode lumens 64.Alternatively, the embolic particles 170 may be delivered by anothertubular delivery member that is positioned within the lumen 64 of theneedle electrode 26. The embolic particles 170 may also be delivered ina liquid solution, such as saline. In this cause, the embolizationactuator 8 may include a syringe or a pump for delivering the liquidsolution, as similarly-discussed previously with reference to FIG. 7B.An example of the type of embolic particles 90 that may be use is theContour®-PVA particles, available from the Boston ScientificCorporation. The embolic particles 170 may have a wide range of sizes.The Contour-PVA particles have particle sizes that range from 45–150 to1000–1180 microns. Embolic particles 170 having other sizes may also beused, depending on the particular application. In one embodiment, theembolic particles 170 are spherical in shape. In alternativeembodiments, the embolic particles 170 may have other geometric shapesand/or irregular shapes.

FIG. 7D shows the needle electrode 26 delivering an occlusion balloon174 (the occlusive element 9) to a site. The balloon 174 may bedetachably coupled (for permanent occlusion of a site) or non-detachablycoupled (for temporary occlusion of a site) to at the distal end 180 ofan inflation tube 176 disposed within the electrode lumen 64.Alternatively, the corresponding electrode lumen 64 and shaft lumen 72may acts as the inflation tube. The inflation tube 176 delivers aninflation medium to an interior 178 of the balloon 174 for inflation ofthe balloon 174. In this case, the embolization actuator 8 may include apump, a syringe, or other medium delivery device for delivering theinflation medium to the interior 178 of the balloon 174. The balloon 174is preferably made of a thermoplastic or elastomeric materials, such aspolyimide (kapton), polyester, silicone rubber, nylon, mylar,polyethelene, or polyvinyl chloride. However, other elastic materialsknown in the art may also be used for construction of the balloon 174.Medical balloons have been described in U.S. Pat. No. 5,925,083, theentirety of which is hereby incorporated by reference. It should benoted that the shape of the balloon 94 is not necessarily limited tothat illustrated in the figure. Other designed shapes may also be used.Furthermore, the size of the balloon 174 may vary, depending on theparticular application. For example, a relatively larger balloon 174 maybe used to occlude a large vessel, while a smaller balloon 94 may beused to occlude a smaller vessel.

FIG. 7E shows the needle electrode 26 delivering to a site a nonporousfilter 182 (the occlusive element 9) that is secured to a wire 184 at adistal end 186. In this case, the embolization actuator 8 includes thewire 184, which may be used to distally advance the filter 182 withinone of the electrode lumens 64 out through the corresponding outlet port68. The filter 182 may be used to slow blood flow in a vessel. Thefilter 182 may be made of a variety of materials, such as nylon,polymer, plastics, and/or metals. In one embodiment, the filter 182 ismade at least partially from Nitinol, which allows the filter 182 tounfold itself to form a membrane when outside the lumen 64 of the needleelectrode 26, and be stretched or folded into a low profile when residedwithin the lumen 64. Deployment of the filter 182 may be accomplished bydistally advancing the wire 184 that is placed within the lumen 64 ofthe needle electrode 26.

It should be noted that the occlusion element 9 that may be delivered bythe needle electrode 26 should not be limited to the examples discussedpreviously, and that other occlusion elements may also be used so longas they are capable of at least partially occluding a site, such as avessel.

FIGS. 8A and 8B shows another probe assembly 200 that can be used in thepreviously described system 2. The probe assembly 200 is similar to thepreviously described probe assembly 4, with the exception that itcomprises a different means for indexing which of the needle electrodes26 will be used to embolize the blood vessel. Specifically, the probeassembly 200 includes a shaft 201 having a distal end 202, a proximalend 204, and a lumen 206 extending between the distal and proximal ends202 and 204. The electrodes 26 are carried on the distal end 202 of theshaft 201, and may be deployed by distally advancing the shaft 201relative to the cannula 12. The probe assembly 200 also includes anindexer 208 having a distal end 210, a proximal end 212, and a lumen 214extending between the distal and proximal ends 210 and 212. The indexer208 is configured to be placed within the lumen 206 of the shaft 201,and may be rotated about a longitudinal axis 213 of the shaft 201. Inparticular, the indexer 208 may be rotated such that the lumen 214 ofthe indexer 208 is in communication with one of the lumens 64 of theelectrodes 26. A handle 216 that secures to the proximal end 212 of theindexer 208 may be provided to facilitate manipulation of the indexer208. Optionally, a marker (not shown) may be placed on the handle 216and/or on the proximal end 212 of the indexer 208 for indicating arotational orientation or a position of the handle 216 relative to theshaft 201 (and the electrodes 26) during use.

Referring now to FIGS. 9A–9E, the operation of the tissue ablationsystem 2 is described in treating a treatment region TR within tissue Tlocated beneath the skin or an organ surface S of a patient. The tissueT prior to treatment is shown in FIG. 9A. The cannula 12 is firstintroduced within the treatment region TR, so that the distal end 14 ofthe cannula 12 is located at the target site TS, as shown in FIG. 9B.This can be accomplished using any one of a variety of techniques. Insome cases, the cannula 12 and shaft 20 may be introduced to the targetsite TS percutaneously directly through the patient's skin or through anopen surgical incision. In this case, the cannula 12 may have asharpened tip, e.g., in the form of a needle, to facilitate introductionto the target site TS. In such cases, it is desirable that the cannula12 be sufficiently rigid, i.e., have a sufficient column strength, sothat it can be accurately advanced through tissue T. In other cases, thecannula 12 may be introduced using an internal stylet that issubsequently exchanged for the shaft 20 and electrode array 27. In thislatter case, the cannula 12 can be relatively flexible, since theinitial column strength will be provided by the stylet. Morealternatively, a component or element may be provided for introducingthe cannula 12 to the target site TS. For example, a conventional sheathand sharpened obturator (stylet) assembly can be used to initiallyaccess the tissue T. The assembly can be positioned under ultrasonic orother conventional imaging, with the obturator/stylet then removed toleave an access lumen through the sheath. The cannula 12 and shaft 20can then be introduced through the sheath lumen, so that the distal end14 of the cannula 12 advances from the sheath to the target site TS.

After the cannula 12 is properly placed, the shaft 20 is distallyadvanced to deploy the electrode array 27 radially outward from thedistal end 14 of the cannula 12, as shown in FIG. 9C. The shaft 20 willbe advanced sufficiently, so that the electrode array 27 fully everts inorder to circumscribe substantially the entire treatment region TR, asshown in FIG. 9D. Alternatively, the needle electrodes 26 may be onlypartially deployed or deployed incrementally in stages during aprocedure.

As shown in FIG. 9E, the needle electrodes 26 are deployed such that oneof the needle electrodes 26 (the occlusion electrode) penetrates a wallof a vessel V adjacent the treatment region TR. The radio-opaque markers66 carried at the distal ends 60 of the needle electrodes 26 and/or themarkers (if they are provided) may be used to assist deploying one ofthe needle electrodes 26 such that its tip penetrates the wall of thevessel V. If the tip 58 of one of the needle electrodes 26 is unable toreach the vessel V, the needle electrodes 26 may be retracted andre-deployed at different orientation by torsionally rotating the probeassembly 4 (or 200). Alternatively, the probe assembly 4 (or 200) may beremoved from the patient, and re-inserted into the patient at adifferent location such that deployment of the needle electrodes 26 mayallow one of the needle electrodes 26 to reach the vessel V. In afurther alternative, the system 2 may further include a stylet that canbe inserted through the delivery port 100 of the handle member 28 (ifone is provided), the delivery lumen 72, and then through the lumen 64of one of the electrodes 26. The stylet serves as an extension of theneedle electrode 26, and may be used to penetrate the wall of the vesselV. The stylet may have a substantially rectilinear shape, oralternatively, may have a variety of pre-formed shapes. The stylet maybe made from any of the materials described previously with reference tothe needle electrodes 26.

After the distal end 66 of one of the electrode 26 is placed within thelumen of the vessel V, the delivery port 100 is aligned with thedelivery lumen 72 corresponding to the lumen 64 of the electrode 26 thathas been placed within the vessel V. Specifically, if the handle member28 is used, the handle member 28 may be rotated about a longitudinalaxis of the shaft 20 to align the port 100 with one of the deliverylumens 72 or with one of the electrode lumens 64, which corresponds tothe electrode 26 placed within the lumen of the vessel V. If the indexer208 is used, the indexer 208 may be rotated about a longitudinal axis ofthe shaft 201 to align the lumen 214 of the indexer 208 with theelectrode lumens 64 which corresponds to the electrode 26 placed withinthe lumen of the vessel V. A marker located at the handle member 28 (orthe indexer 208) and/or the shaft 20 (or 201) may be used to indicatethe orientation or position of the handle member 28 (or the indexer 208)relative to the shaft 20 (or 201). A contrast agent may be deliveredthrough the port 100 to verify that the position of the port 100corresponds to the desired needle electrode 26. Radio-opaque markers 66(if they are provided) carried at the distal ends of the electrodes 26may also be used to identify the desired electrode 26.

After the desired electrode 26 has been verified, the RF generator 6 isthen connected to the probe assembly 4 (or 200) via the electricalconnector 38. If the system 2 includes the embolization actuator asdiscussed previously, the embolization actuator may also be connected tothe delivery port 100 of the handle member 28 for delivery of theocclusion element 9 through the delivery port 100, through the indexedshaft lumen 72, and then out through the lumen 64 of the electrode 26(FIG. 9E). If the alternative probe assembly 200 is instead used, theocclusion element 9 is delivered through the lumen 214 of the indexer208, and then out through the lumen 64 of the electrode 26 into thelumen of the vessel V. Thus, it can be appreciated that the electrode 26serves as a delivery catheter that delivers the occlusion element 9 tothe lumen of the vessel V in a manner similar to any of the knownconventional methods.

The insertion of the occlusion element into the vessel V reduces orprevents substantial blood flow through the vessel V, thereby reducingthe possibility that bloodflow may draw produced heat away from thevessel wall during ablation of the treatment region TR. Any of theocclusion elements discussed previously may be used. The occlusion ofthe vessel V may or may not be permanent. For example, one or moreembolic coils 160, liquid embolic 168, occlusion balloon 174 that isdetachable, and/or the embolic particles 170 may be delivered to thevessel V to permanently occlude the vessel V. Alternatively, occlusionballoon 174 that is non-detachable, filter 182, bioabsorable agents, ortethered coils may be used to temporarily occlude the vessel V.

After the vessel V has been desirably occluded, the RF generator 6 isoperated to deliver ablation energy to the needle electrodes 26 eitherin a unipolar mode or a bipolar mode. As a result, the treatment regionTR is necrosed, thereby creating a lesion on the treatment region TR.

In one preferred method, all of the needle electrodes 26 are used todeliver ablation energy. Alternatively, all of the needle electrodes 26except the one that was used to deliver the occlusion element are usedto deliver ablation energy. In this case, the generator 6 may beconfigured such that it could allow a user to selectively choose whichof the needle electrodes 26 to activate.

Because the vessel V adjacent the treatment region TR is occluded, theprobe assembly 4 (or 200) allows ablation of the tissue surrounding thevessel V without substantial heat loss, thereby reducing the possibilityof having incomplete necrosis of the tissue surrounding the vessel V. Inmany cases, a single ablation may be sufficient to create a desiredlesion. However, if it is desired to perform further ablation toincrease the lesion size or to create lesions at different site(s)within the treatment region TR or elsewhere, the needle electrodes 26may be introduced and deployed at different target site(s), and the samesteps discussed previously may be repeated. When a desired lesion attreatment region TR has been created, the needle electrodes 26 areretracted into the lumen 18 of the cannula 12, and the probe assembly 4is removed from the treatment region TR.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

1. A medical probe assembly for ablating tissue, comprising: anelongated shaft having a proximal end and a distal end; a handleconnected to the proximal end of the elongated shaft and comprising adelivery port; a plurality of electrodes carried by the elongated shaft,each electrode comprising an electrode lumen; and an indexer configuredto selectively place the delivery port in communication with one of theelectrode lumens.
 2. The medical probe assembly of claim 1, wherein theindexer is rotatable about a longitudinal axis of the elongated shaft.3. The medical probe assembly of claim 1, wherein the indexer isconfigured to place the delivery port in direct communication with theselected electrode lumen.
 4. The medical probe assembly of claim 1,wherein the indexer is configured to place the delivery port in indirectcommunication with the selected electrode lumen.
 5. A tissue ablationsystem, comprising: a probe assembly comprising a plurality of ablationelectrodes, each electrode comprising a lumen; an occlusion elementselected from the group consisting of an embolic coil, liquid embolic,an occlusion balloon, embolic particles, and a filter; an actuator forcausing delivery of the occlusion element through a selected electrodelumen; and an indexer configured to place the actuator in communicationwith a selected electrode lumen.